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Monday, September 20, 2010

I was running Windows XP SP3 as a guest in a virtual machine (VM) in VMware Workstation 7.1.1 on an Ubuntu 10.04 (Lucid Lynx) host. I had just installed a couple of freeware utilities when suddenly Windows Explorer began refreshing itself about every two seconds. More specifically, it was refreshing the right-hand pane, showing files and folders, but not the left pane, showing the folder tree.

I thought at first it was a virus, but I was running antivirus software, and a scan with a different antivirus program turned up nothing. Besides, I had just downloaded those programs from reputable sources (e.g., CNET) that supposedly certified them to be virus-free.

A search suggested this was a relatively common problem. Several posts made me think it had to do with network drives, which in this case would mean the link between Windows and VMware. I killed the VM, reverted to a previous snapshot, and started that, but the same thing was happening there as well. I powered up a different VM in a different session of Workstation. The problem was not occurring there. I closed all sessions of Workstation and powered up the misbehaving VM in a new session of Workstation. The problem recurred -- but then, after a minute or two, it stopped. But then, after I used Windows Explorer some more, it resumed; but then it stopped again.

I downloaded the "Prevent Automatic Folder and Icon Refresh" registry edit from Kelly's Korner and ran that, and then rebooted Windows within the VM. The problem was still there. I took this to mean that *automatic* refresh was not the problem -- that, presumably, something was manually refreshing Explorer.

I tried displaying different drives' contents in Explorer, on the theory that maybe this was happening in connection with just one particular network drive. That was not the case; it happened on all of them.

I wondered if a program installation was responsible for the problem. But it was not clear to me how any of these would have been responsible for the fact that the flashing occurred within a snapshot that I had taken before installing them.

Then I came closer to what seemed like a possible answer. I tried again to install the Microsoft Task Switch Powertoy. I had tried before, and it had given me an error message, and the same thing happened again. The error message was "Error 1606. Could not access network location [gibberish]." The gibberish was actually just a set of five squares with no characters in them. It appeared that the installer was trying to access a network location whose name did not consist of valid characters. Following advice, I checked the following registry keys for incorrect addresses:

I did find several bad entries in the second of those five locations. I corrected those and rebooted the VM. I was now able to install the PowerToy. Unfortunately, the flashing was still going on. I went into VM > Settings > Options > Shared Folders and switched that to Disabled > Save. The flashing stopped. In Windows Explorer, I tried to go to another network drive, but got the message that it "is not accessible. The network path was not found." I went to drive C (not a network drive). Its contents displayed OK. No flashing. I set Shared Folders back to Always Enabled. No flashing on drive C. Flashing on drive D. I tried C again. The folders there would refresh once, immediately after being selected, but then not again. In Windows Explorer's menu, I went to Tools > Disconnect Network Drive and disconnected drive D. Drive E was still flashing. I went to Tools > Map Network Drive and mapped D again. It was flashing.

A Microsoft Knowledgebase webpage said that a somewhat related problem (flickering in the left-hand pane of Windows Explorer) could be repaired at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer. I had only a lowercase "policies" (not "Policies") key at that location. Regedit would not let me create the uppercase version. So I went into the lowercase "policies" key. It did have an Explorer subkey. I went in there and created a new key, NoRemoteRecursiveEvents, of REG_DWORD type, and gave it a value of 1. I exited regedit and rebooted. This step did not solve the problem.

I closed this VM and went back to the previous version, the one that did not flash. I corrected the incorrect registry addresses (above) first. Then I started reinstalling the programs that I had been installing when the problem began. I went down the list and, what do you know, the flickering started when I installed FolderSize, and it stopped when I uninstalled it. FolderSize calculates the size of folders, and apparently refreshes the screen while it does so. After I uninstalled it, the problem went away.